ESXi includes a firewall between the management interface and the network. The firewall is enabled by default.

At installation time, the ESXi firewall is configured to block incoming and outgoing traffic, except traffic for the default services listed in TCP and UDP Ports for Management Access.

Note

The firewall also allows Internet Control Message Protocol (ICMP) pings and communication with DHCP and DNS (UDP only) clients.

Supported services and management agents that are required to operate the host are described in a rule set configuration file in the ESXi firewall directory /etc/vmware/firewall/. The file contains firewall rules and lists each rule's relationship with ports and protocols.

You cannot add a rule to the ESXi firewall unless you create and install a VIB that contains the rule set configuration file. The VIB authoring tool is available to VMware partners.

Note

The behavior of the NFS Client rule set (nfsClient) is different from other rule sets. When the NFS Client rule set is enabled, all outbound TCP ports are open for the destination hosts in the list of allowed IP addresses. See NFS Client Rule Set Behavior for more information.